initial

ast/ast.go

@@ -0,0 +1,44 @@
+package ast
+
+import (
+  "fmt"
+  "strings"
+)
+
+type AST struct {
+  Tag Tag
+  Val interface{}
+}
+
+type Tag int8
+
+const (
+  Symbol Tag = iota
+  List
+  String
+  Num
+  Bool
+)
+
+func (tag Tag) String() string {
+    names := []string{
+        "Symbol",
+        "List",
+        "String",
+        "Num",
+        "Bool",
+    }
+
+    return names[tag]
+}
+
+func (ast AST) Pretty() string {
+  if ast.Tag == List {
+    var agg []string
+    for _, elem := range(ast.Val.([]AST)) {
+      agg = append(agg, elem.Pretty())
+    }
+    return "(" + strings.Join(agg, " ") + ")"
+  }
+  return fmt.Sprintf("%v", ast.Val)
+}